Combined impacts of land change and climate variability on ecosystem net primary productivity in arid regions

Abstract

Net Primary Productivity (NPP) is an index for assessing ecosystem services and productivity on land. However, previous studies focused solely on NPP changes across ecological regions, overlooking the comparative advantage of the impacts of land changes and climatic variations on various forms of NPP as indicators of ecosystem degradation and restoration across different eco-political milieux. This study comparatively analyzed land cover changes and examined NPP trends and their effects using Mann-Kendall Theil-Sen slopes, the Pearson correlation, and advanced geostatistical methods in the Lake Chad Basin (LCB) and the Aral Sea Basin (ASB). We found that from 2000 to the present and projected to 2030, cropland is expected to expand by 2.20 %, leading to a reduction of shrubland by −2.40 % in LCB. Likewise, a probable increase of 1.1 % in grassland is expected to further reduce waterbodies in ASB by −1.5 %. These potential changes are the resultant effect of the present human-induced NPP (HNPP) reduction of −5.92gC/m2/yr across 2.44 × 103 km2 and 29.84gC/m2/yr across 14.32× 103 km2, indicating human-dominated degradation (HDD) in LCB. Whereas, in ASB, the influence of HNPP by −8.12 gC/m2/yr across 14.32 × 103 km2 and by 4.00gC/m2/yr across 7.24× 103 km2 indicate incipient human-dominated restoration scenarios. Consequent to the warming temperature, climate fluctuations are characterized by HDD in LCB, whereas in ASB, they are characterized by climate-induced degradation. Apprehending these evolving dynamics in endorheic lakes can provide insight into potential restoration trajectories for future land degradations.